What is Skin-On Interfaces?

Skin-On Interfaces are sensitive skin-like input methods than can be added to existing devices to increase their capabilities.
When we interact with others, we use skin as interfaces. However the objects of mediated communication - such as the smartphone - still has a cold interface that doesn't allow natural interaction and input.
In this project, I wanted to make available the perfect human interface that is the skin for existing devices.

Reproducing the skin layers

I followed a bio-driven approach where I took inspiration from the human skin to design the perfect artificial skin.

From a sensory point of view, I study how to reproduce the visual, tactile and kinesthetic aspects of the human skin. I used the silicone to mimic the skin deformability with reference to relevant literature. I investigate how visual factors (color) and haptic factors (texture and thickness) impact user experience and the perception of realism.

From a gestural point of view, I explore how gestures naturally performed on the skin can be transposed to Skin-On interfaces. I use this knowledge to propose a series of gestures that are desirable for Skin-on interfaces (e.g. multitouch touch, pressure and complex gestures such as strokes, stretching or grabbing).

From a sensing point of view, I try to reproduce a skin sensing layer that can track natural gestures with a spatial acuity comparable to human skin.

Easy fabrication process for replication

The fabrication process is fairly simple and can be reproduced easily by other researches and HCI practitioners. You can find a more detailed version here.

1.Creating the top textured layer. The epidermis layer is built by pouring DragonSkin silicone with beige pigments on a skin-like texture mold.

2.Positioning the electrodes. Once cured, the top layer is positioned on a pane, with the texture facing down. I used conductive yarn (Datastretch) placed in a perpendicular grid on top of the artificial epidermis to form the electrodes.

3.Adding hypodermis. We prepare a rectangular mold of the size of the desired artificial skin and place it on top of the sensing layer. The hypodermis viscous silicone layer of Ecoflex Gel is poured inside the mold to reach the desired fat thickness, i.e. 10mm in this example.

4.Connecting electronics. The electrodes are then connected, i.e. they are soldered to the hardware sensing platform. Buy it here.

5.Shaping the Skin-On. To improve the visual appearance of the interface, the excess of silicone can be trimmed before being folded around the side of the hypodermis layer and glued with silicone glue. Paint or makeup can be added to shade the artificial skin with flesh like tonal variation, thus increasing anthropomorphism.

Trial and erros

The fabrication process went through a lot of trial and errors, resulting sometimes

Open-Source and Open Hardware

I developed an Open Source and Open Hardware multitouch controller to enable DIY fabrication of multi-touch interfaces on unconventional surfaces such as human skin: The MuCa-Breakout. Buy it here.

The breakout is composed of a controller which allows for connecting 12 sensing electrodes and 21 transmitting electrodes. Any conductive electrode with an unusual shape or using unusual material can be used for sensing and transmitting. The touch controller can transmit the raw electrodes data or 5 multi-touch coordinates via i2C, to any micro-controller. You want to try one unit? Contact me!